Transmission auxiliary box seal system

ABSTRACT

The present invention provides a transmission including a main gear box and an auxiliary gear box secured to the main box. The auxiliary gear box includes an auxiliary shaft supporting an auxiliary gear with a clutch collar support on the auxiliary shaft adjacent to the auxiliary gear. The clutch collar is selectively actuatable between engaged and disengaged auxiliary gear positions. A piston housing is connected to the auxiliary gear box and supports solenoids fluidly connected to a piston on a shift shaft. The auxiliary box includes a bore therein supporting the shift shaft. The shift shaft is moveable axially between first and second positions in response to actuation of the solenoids corresponding to the engage and disengaged auxiliary gear positions. The shift shaft supports a shift for that coacts with the shift collar. The shift shaft includes an annular groove and a seal is arranged in the annular groove between the auxiliary box housing and the shift shaft for separating transmission fluid from actuating fluid within the piston.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a seal system for atransmission, and more particularly, the invention relates to a sealsystem for a shift shaft of an auxiliary box.

[0002] Transmissions for commercial vehicles have a large number ofgears through which the vehicle operator shifts as the vehicle travelsunder various load and grade conditions. The transmission may be manualor automated manual. A typical commercial vehicle transmission includesa main gear box through which the operator shifts using a transmissionshift lever. An auxiliary gear box is attached to the main gear box toprovide gear ratios in addition to those provided by the main gear box.The gears of the auxiliary gear box may be shifted with hydraulic orpneumatic actuators in response to the vehicle operator manipulatingelectronic buttons or switches in the vehicle cab, which may be locatedon the shift lever.

[0003] For auxiliary gear boxes utilizing pneumatic actuators, a pistonhousing is secured to the auxiliary gear box. Solenoids are connected tothe piston housing and control the flow of air into the piston housingto control the actuators. The actuators include a shift shaft with apiston secured thereto, which is disposed within an air chamber. Theshift shaft is supported by the auxiliary box housing, and the pistonmay be arranged in either the auxiliary box or piston housing. Thesolenoids control the flow of air to either side of the piston to movethe shift shaft axially. The shift shaft includes a shift fork supportedthereon which engages a clutch collar in the auxiliary gear box thatselectively engages the auxiliary gears in response to axial movement ofthe piston.

[0004] A seal is used between the shift shaft and auxiliary box housingto separate the pressurized air within the air chamber and thetransmission oil within the auxiliary gear box. An annular groove ismachined into the bore of the auxiliary box housing supporting the shiftshaft. Typically, an O-ring is arranged within the annular groove.Because the annular groove is located within the bore, it is difficultto machine. Moreover, the O-ring may not provide an acceptable seal.Therefore, what is needed is an improved seal system for an auxiliarygear box housing that is easier to machine and provides a more effectiveseal.

SUMMARY OF THE INVENTION

[0005] The present invention provides a transmission including a maingear box and an auxiliary gear box secured to the main box. Theauxiliary gear box includes an auxiliary shaft supporting an auxiliarygear with a clutch collar support on the auxiliary shaft adjacent to theauxiliary gear. The clutch collar is selectively actuatable betweenengaged and disengaged auxiliary gear positions. A piston housing isconnected to the auxiliary gear box and supports solenoids fluidlyconnected to a piston on a shift shaft. The auxiliary box includes abore supporting the shift shaft. The shift shaft is moveable axiallybetween first and second positions in response to actuation of thesolenoids corresponding to the engage and disengaged auxiliary gearpositions. The shift shaft supports a shift for that coacts with theshift collar. The shift shaft includes an annular groove, and a seal isarranged in the annular groove between the auxiliary box housing and theshift shaft for separating transmission fluid from actuating fluidwithin the piston.

[0006] Accordingly, the above invention provides an improved seal systemfor an auxiliary gear box housing that is easier to machine whileproviding a more effective seal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Other advantages of the present invention can be understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

[0008]FIG. 1 is a perspective end view of a commercial vehicletransmission having an auxiliary gear box;

[0009]FIG. 2 is a cross-sectional view of the auxiliary box and pistonhousings taken along line 2-2 of FIG. 1; and

[0010]FIG. 3 is an enlarged cross-sectional view of the auxiliary boxhousing and shift shaft shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0011] A transmission 10 is shown in FIG. 1. A commercial vehicletransmission 10 typically includes a main gear box 12 and an auxiliarygear box 14 secured to the main gear box 12. The main gear box 12provides gears that, when shifted by the shift lever, provide a largenumber of gear ratios. The transmission 10 may be a manual or automatedmanual transmission. Additional gear ratios are provided by manipulatingthe auxiliary gear box 14, which “splits” or extends the “range” of thegear ratios provided by the main gear box 12.

[0012] The auxiliary gear box 14 also may be automated by utilizinghydraulic or pneumatic actuators. For such an automated system, a pistonhousing 16 is secured to the auxiliary gear box 14. Solenoids 18 and 19are supported on the piston housing 16 and selectively provide apressurized fluid to the piston housing 16 for shifting the gears of theauxiliary gear box 14. Referring to FIG. 2, a shift shaft 20 issupported within a bore 22 of the auxiliary box housing 14. A shift fork24 is supported on the shift shaft 20 and engages a clutch collar 26. Asis known in the art, the clutch collar 26 is supported on an auxiliarygear shaft 28 and is moved to selectively engage an auxiliary gear 30.The shift shaft 20 is actuated along an axis A to engage and disengagethe clutch collar 26 from the auxiliary gear 30.

[0013] The splitter shaft is shown in FIG. 2. The shift shaft 20 has anend arranged within an air chamber 32, which is defined by the auxiliarybox housing 14 for a splitter shaft arrangement. For the range shaft,the air chamber may be defined by the piston housing for easiermachining and assembly. The end of the shaft 20 has a piston 34 securedthereto by a fastener 36 to divide the chamber 32 into first 38 andsecond 40 cavities. The solenoids 18, 19 regulate the flow of fluid intothe cavities 38, 40 through first 39 and second 41 passages,respectively. The piston housing 16 is secured to the auxiliary boxhousing 14 by fasteners (not shown) to enclose the air chamber 32. Theshift shaft 20 moves axially along axis A in response to changes in thepressures in the cavities 38, 40 regulated by the solenoids 18, 19. Theshift shaft 20 may be held in a desired position by a detent assembly46.

[0014] In the prior art, the air chamber 32 was sealed from the interiorof the auxiliary gear box 14 by an O-ring arranged in an annular groovemachined in the auxiliary box housing bore 22. The groove was difficultto machine in the auxiliary box housing since it was located interiorlyof the end of the bore 22, which make it difficult to position amachining tool. Moreover, the O-ring provided an insufficient sealbetween the pressurized air chamber 32 and the transmission fluid withinthe auxiliary gear box 14. To this end, the present invention providesan annular groove 48 machined onto the shift shaft 20. A seal 50 isarranged in the annular groove 48, as best shown in FIG. 3.

[0015] The annular groove 48 may be easily machined onto the shift shaftand the seal 50 installed thereon. The shift shaft 20 with the seal 50may then be inserted into the bore 22 in the auxiliary box housing 14.Preferably, a lip seal is arranged in the annular groove 48. A lip sealincludes a wiper 52 that extends to the bore 22 to scrape oil from thebore 22 as the shift shaft 20 moves axially thereby preventing it fromentering the air chamber 32. Opposite the wiper 52, the seal 50 mayinclude a notch 54 defining opposing walls 56 and 58. Pressurized fluidin the notch 54 forces the opposing walls 56, 58 outwardly away from oneanother to create a seal between the shaft 20 and auxiliary box housing14 to better retain the pressurized fluid within the air chamber 32.

[0016] The invention has been described in an illustrative manner, andit is to be understood that the terminology that has been used isintended to be in the nature of words of description rather than oflimitation. Obviously, many modifications and variations of the presentinvention are possible in light of the above teachings. It is,therefore, to be understood that within the scope of the appended claimsthe invention may be practiced otherwise than as specifically described.

1. A transmission comprising: a main gear box; an auxiliary gear boxsecured to said main gear box including an auxiliary shaft supporting anauxiliary gear, and a clutch collar supported on said auxiliary shaftadjacent to the auxiliary gear selectively actuatable between engagedand disengaged auxiliary gear positions, said auxiliary box having abore; a piston housing connected to said auxiliary gear box supportingsolenoids; a shift shaft disposed within said bore movable axiallybetween first and second positions in response to actuation of saidsolenoids corresponding to engaged and disengaged auxiliary gearpositions, said shift shaft supporting a shift fork that engages saidclutch collar, said shift shaft having an annular groove; and a sealdisposed in said annular groove engaging said auxiliary box housing andsaid shift shaft for separating transmission fluid from actuating fluid.2. The transmission according to claim 1, wherein said auxiliary boxhousing includes an air chamber, and said shift shaft includes an enddisposed in said air chamber with said annular groove arranged betweensaid shift fork and said air chamber.
 3. The transmission according toclaim 2, wherein said end includes a piston with said piston disposed insaid air chamber.
 4. The transmission according to claim 1, wherein saidseal is a lip seal.
 5. The transmission according to claim 4, whereinsaid lip seal includes a wiper and a notch opposite said wiper definingopposing walls.
 6. The transmission according to claim 1, wherein theshift shaft defines an axis with said shift shaft translating along saidaxis between said first and second positions.
 7. A transmissioncomprising: an auxiliary box housing having a bore; a shift shaftdisposed within said bore moveable axially between first and secondpositions, and an annular groove arranged in a circumference of saidshift shaft proximate to said end; and a seal disposed in said annulargroove engaging said auxiliary box housing and said shift shaft.
 8. Thetransmission according to claim 7, wherein an air chamber arrangedadjacent to said bore, and end of said shift shaft includes a pistonsecured thereto with said piston disposed in said air chamber.
 9. Thetransmission according to claim 8, wherein said auxiliary box housingincludes said air chamber.
 10. The transmission according to claim 7,wherein said seal is a lip seal.
 11. The transmission according to claim10, wherein said lip seal includes a wiper and a notch opposite saidwiper defining opposing walls.